This research program project includes the following studies: 1. Normal Development of Nervous System in Humans, to be carried out on the embryos and fetuses of the Carnegie Collection and on others to be collected, and including detailed studies of: (a) The normal sequence of development of the central and peripheral nervous systems, skull, and vertebrae in staged embryos, emphasizing light and electron microscopic, and histochemical methods, so as to provide an accurate baseline for the analysis of congenital defects and malformations. (b) The development and growth of the corpus callosum and pyramidal tracts, which first appear during the fetal period, so as to gain insight into the mechanisms whereby axons grow through parts of the nervous system which are already highly organized and actively functioning. (c) Histological and radiological features of the normal growth and maturation of the fetal spinal cord and vertebral column and their correlation with congenital malformations. 2. Normal Development of Nervous System in Non-Human Primates, using the material of the Carnegie Collection and the California Primate Research Center, and including: (a) Staging of primate embryos so as to lay the basis for morphological and experimental studies. (b) Study normal development, as in la above, including the development of the eye. (c) Radioautographic studies of placodes and caudal proliferation center, and ontogenesis of acetylcholinesterase isoenzymes. 3. Teratological Studies. These will be carried out at the California Primate Research Center and will include the development of experimental models, using teratogenic agents in pregnant monkeys: (a) Malformations of the nervous system, skull, and vertebrae. (b) Defects of the nervous system associated with limb defects caused by Thalidomide. 4. Computerization of Data Storage and Retrieval (feasibility study). 5. Planning for Clinicopathological Studies.